Estimates for last Sunday’s 20th Sprint Cup race on the famed 2 ½-mile oval went as low as 75,000 – which is about 25 percent of capacity.

When NASCAR first visited Indianapolis in 1994, the tickets were harder to come by than those for the Indianapolis 500. The Brickyard 400 easily eclipsed the “Super Bowl” Daytona 500 as NASCAR’s most attended race.

And the love affair between NASCAR fans and the world’s most famous track lasted for a decade.

But attendance has plunged dramatically annually since around 2005 to a point where neither NASCAR nor IMS officials any longer post attendance estimates – and ESPN goes out of its way to avoid camera angles that show empty seats.

Meanwhile, as interest in the Brickyard 400 wanes, attendance for the track’s foundation event, the Indianapolis 500 is growing again back to pre CART-IRL civil war levels.

What has happened to NASCAR at the Brickyard?

A number of things, including:

Stock cars races on the four-turn, 2 ½-mile oval are boring. There is no other way to put it. While there were 20 lead changes last Sunday – and that is very low by NASCAR standards – only one was under the green flag. Ryan Newman won by 2.6 seconds over Jimmie Johnson. Cars were strung out all around the track. NASCAR fans know the flat layout of the track is not conducive to side-by-side stock car racing.

I don’t know if you have ever been to Indianapolis in the summer, but it can be miserable with high temperatures and humidity to match. Officials at IMS are looking into adding lights so that the Brickyard 400 can be turned into a night race.

The race is shown live on television in the Indianapolis area. Many would-be fans opt to watch from their air-conditioned living rooms.

Plus, there was the one Brickyard turned into a farce when the tires wore out after 10 laps.

NASCAR and IMS are very aware of the sharp decline in Brickyard attendance. NASCAR has moved Saturday’s Nationwide Series race from nearby Indianapolis Raceway Park to the Speedway as well as adding a Grand-American sports car race to bolster the weekend program.

But NASCAR officials last week were critical of IMS for the way the track promotes the race.

Could the Brickyard be yanked from the Sprint Cup schedule? NASCAR officials say no. But NASCAR pulled the second race from Auto Club Speedway in Fontana for poor attendance. Races run in much worse conditions in the heart of the south, say Darlington, S.C., would draw bigger crowds than Indy is getting.

The problem is that NASCAR anointed the Brickyard 400 as the second crown jewel of its series to the Daytona 500 back in 1994. Plugging the plug would be a public relations disaster for a series having the same problems elsewhere.

But the Indy problem is huge. As recently as 2007, the crowd estimate was 270,000. In 2008, it was 240,000. Then came a 60,000 drop in 2009, followed by a 40,000 drop in 2010 to 140,000. The decline has slowed over the past three years – but it hasn’t stopped.

Palmer at Mid-Ohio

San Diego’s Tyler, Palmer, 19, will be racing a Mini Cooper in the Pirelli World Challenge this weekend on the Mid-Ohio road course. Palmer is coming off three podium finishes in as many races during his first visit to Lime Rock, Conn.

Although this is Palmer’s first year in the Pirelli World Challenge series, he has won two national championships in his two previous visits to Lexington, Ohio, while racing in the Porsche 944 Spec Class.

Checkered Flag

Ron Capps:The Carlsbad driver moved into second in Funny Car points by defeating John Force for the NHRA championship last Sunday in Sonoma. It was Capps’ second win of the season.